In the conventional process for composting organic materials, the general practice has been to store or pile the organic materials to be composted for a certain period and to periodically turn them over at a proper time interval to promote aerobic fermentation, a proper amount of air being preferably fed to the stored materials from the bottom thereof during the storage which may be omitted if the materials are stored in the open air depending on the conditions such as the local or regional climate or environment. At any rate, an operation for plowing or turning the piled materials over is indispensable in order to uniformly mix the materials as well as to fractionalize the materials so as to substantially increase the total area of the surface of the materials exposed to air.
On the other hand, it is necessary to displace the materials in a predetermined direction simultaneously with the plowing up or turning over operation if the composting operation is to be made continuous.
In an apparatus disclosed in PCT application No. (PCT/JP78/00006) assigned to the Ebara Corporation, the aim was to increase the processing capacity of a multi-stage composting apparatus per unit area required for the installation and the apparatus has been admitted as satisfactory, for its intended purposes. However, due to its construction, the driving mechanism therefor is complex and the configuration has been limited to a circular base area. Sometimes, this construction may increase the operation cost and/or maintenance cost and may not be proper for use in a place where limitation on the field space is substantially neglegible.
In other conventional type composting systems, an inherent disadvantage is that the necessary agitating and displacing device for performing the continuous composting operation becomes large as the capacity of the apparatus is increased, since an increase in the amount of materials to be received and stored in the apparatus necesitates an increase in capacity. Such increased capacity also causes an increase in the expense required for installation and maintenance of the apparatus. In view of the facts encountered in the composting apparatus of the prior art, there has been a great and constant need to provide a method and an apparatus which can handle a large quantity relatively economically.